Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

The present invention provides endovascular devices and the methods of
making and using the same.

Claims:

1. A prohealing endovascular device, comprising a surface generated by a
method comprising: irradiating a surface of the endovascular device with
a high energy radiation for a period of time to cause the surface to
become a super hydrophilic surface.

2. The endovascular device of claim 1, wherein the high energy radiation
is ultraviolet.

4. The endovascular device of claim 1, having an increased rate of
endothelialization as compared with an endovascular device without
treatment by irradiation.

5. The endovascular device of claim 1, having an increased rate of
neointima coverage as compared with an endovascular device without
treatment by irradiation.

6. The endovascular device of claim 1, having an increased affinity of
the device with a native vascular tissue as compared with an endovascular
device without treatment by irradiation.

7. The endovascular device of claim 1, having a reduced friction during
the insertion or delivery of the endovascular device.

8. The endovascular device of claim 1, having a decreased level of
inflammation response at a site receiving the endovascular device as
compared with an endovascular device without treatment by irradiation.

9. The endovascular device of claim 4, wherein the rate of
endothelialization is increased by at least 10%.

10. The endovascular device of claim 5, wherein the rate of neointima
coverage is increased by at least 10%.

11. The endovascular device of claim 6, wherein the affinity is increased
by at least 10%.

12. The endovascular device of claim 7, wherein the friction is decreased
by at least 10%.

13. The endovascular device of claim 8, wherein the level of inflammation
response is decreased by at least 10%.

14. The endovascular device of claim 1, wherein the method further
comprises surface-treating the endovascular device prior to irradiating
the surface of the endovascular device.

18. A method of generating an endovascular device according to claim 1,
comprising: irradiating a surface of the endovascular device with a high
energy radiation for a period of time to cause the surface to become a
super hydrophilic surface, thereby generating the endovascular device.

19. The method of claim 18, further comprising surface-treating the
endovascular device prior to irradiating the surface of the endovascular
device.

21. The method of claim 18, wherein the period is about 10 minutes or
longer.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of PCT/US2010/043152, filed on
Jul. 23, 2010, which claims the benefit of U.S. provisional application
No. No. 61/228,764 filed Jul. 27, 2009. The teaching in these
applications is incorporated hereto in its entirety by reference.

FIELD OF THE INVENTION

[0002] The present invention generally relates to the art of endovascular
devices and the methods of making and using the same.

BACKGROUND OF THE INVENTION

[0003] Current endovascular procedures to treat vascular diseases use a
variety of metallic devices, e.g., guidewires, stents, filters, cage-like
vascular plugs, and coils. One of the most popular materials used for the
endovascular metallic devices is NiTi/Nitinol, so called shape memory
alloy. Although endovascular devices made of NiTi demonstrate a great
performance in human vessels, there are several intrinsic limitations.
Another common metallic material for endovascular device is
Cobalt-Chromium alloy (CoCr), which is often used for stents.

[0004] First limitation is a friction between a metallic device and
catheter. A metallic device is inserted into a plastic catheter, and is
pushed out or twisted in the catheter. In order to reduce the friction,
the inner lumen of catheter or the surface of some metallic guidewire has
a hydrophilic polymer coating. However, such a hydrophilic coating is not
enough to overcome this limitation. The hydrophilic polymer coating comes
off from the device relatively easily. Also certain devices such as a
stent are not easily coated with the hydrophilic polymers. In fact, most
stents are not coated with hydrophilic materials. The friction makes the
delivery of stent or coil into a target lesion difficult and unsafe.
Furthermore, the friction makes it difficult to design a longer stent
because a longer stent would induce an increase in friction so as to be
difficult to deliver to a target lesion. The friction also makes it
difficult to control (twist and push/pull) a metallic guidewire.

[0005] The second limitation is that a patient who receives an
intra-arterial metallic device placement, particularly a metallic stent
placement, is required to be medicated with anti-platelet medications
such as Aspirin or Plavix, so called blood thinners, for several months
in order to prevent clotting and occlusion of stent lumen. The blood
thinners itself carry a risk of spontaneous bleeding in organs such as
brain and gastrointestinal tract. Even with the blood thinning
medications, the clotting of important arteries occurs not infrequently
after the placement of metallic devices in the vessels since the devices
are a foreign material for the human vessels. Although the clotting due
to the intravascular metallic device placement involves a complex
multi-factorial processes, inflammatory reaction and vascular injury are
important factors that activate the coagulation cascade. Furthermore, the
metallic device should be covered with native tissues and cells in the
healing process so that the foreign material does not have a direct
exposure to blood flow.

[0006] Therefore, there is a need for an endovascular device having an
enhanced rate of endothelialization and/or neointima coverage as well as
an enhanced affinity of the device with a native vascular tissue. An
enhanced rate of endothelialization and/or neointima coverage would allow
sooner cessation of blood-thinning medications so as to reduce or
minimize the risk of spontaneous bleeding in organs such as brain and
gastrointestinal tract.

[0007] The embodiments described below address the above identified
problems and needs.

SUMMARY OF THE INVENTION

[0008] According to embodiments of the present invention, it is provided a
prohealing endovascular device, comprising a surface generated by a
method comprising irradiating a surface of the endovascular device with a
high energy radiation for a period of time to cause the surface to become
a super hydrophilic surface.

[0009] The high energy radiation can be any high energy radiation. In some
embodiments, the high energy radiation is ultraviolet.

[0011] The endovascular device of invention has a variety of advantageous
properties. In some embodiments, it has an increased rate of
endothelialization as compared with an endovascular device without
treatment by irradiation, for example, increased by 10%. In some
embodiments, the endovascular device of invention has an increased rate
of neointima coverage as compared with an endovascular device without
treatment by irradiation, for example, increased by 10%. In some
embodiments, the endovascular device of invention has an increased
affinity of the device with a native vascular tissue as compared with an
endovascular device without treatment by irradiation, for example,
increased by 10%. In some embodiments, the endovascular device of
invention has a reduced friction during the insertion or delivery of the
endovascular device, for example, reduced by 10%. In some embodiments,
the endovascular device of invention has a decreased level of
inflammation at a site receiving the endovascular device of invention as
compared with an endovascular device without treatment by irradiation,
for example, decreased by 10%.

[0012] In some embodiments, in combination with any or all of the various
embodiments above, the endovascular device can have a surface treated by
surface-treating the endovascular device prior to irradiating the surface
of the endovascular device.

[0013] The endovascular device can be any endovascular device in medicine
or veterinary medicine. In some embodiments, the endovascular device is
selected from stents, grafts, stent-grafts, catheters, leads and
electrodes, clips, shunts, closure devices, valves, guidewires, filters,
cage-like vascular plug, coils, and particles.

[0014] In some further embodiments of the present invention, it is
provided a method of treating or ameliorating a disorder involving a
vascular condition, comprising implanting in a subject the endovascular
device of the various embodiments disclosed herein. The disorder can be,
e.g., one of atherosclerosis, thrombosis, restenosis, hemorrhage,
vascular dissection, vascular perforation, vascular aneurysm, vulnerable
plaque, chronic total occlusion, patent foramen ovale, claudication,
anastomotic proliferation of vein and artificial grafts, arteriovenous
anastamoses, bile duct obstruction, urethral obstruction and tumor
obstruction.

[0015] In some further embodiments of the present invention, it is
provided a method of generating an endovascular device according to the
various embodiments disclosed herein, the method comprising:

[0016] irradiating a surface of the endovascular device with a high energy
radiation for a period of time to cause the surface to become a super
hydrophilic surface, thereby generating the endovascular device.

The period can be, e.g., about 10 minutes or longer, or about 60 minutes
or longer.

[0017] In some embodiments, the method further comprises surface-treating
the endovascular device prior to irradiating the surface of the
endovascular device. Such surface-treating can be, e.g., treating the
endovascular device by acid-etching, sand-blasting, or machining.

[0019] FIG. 2 shows the mean±SD adsorption rate of bovine serum albumin
after 24 hours of incubation on NiTi surfaces with or without UV
treatment. n=3. **Significantly different from the fresh surface,
p<0.01.

[0021] FIG. 4 shows the mean±SD number of attached endothelial cells to
NiTi surfaces after 6 and 24 hours of incubation. n=3. **Significantly
different from the fresh surface, p<0.01. *Significantly different
from the fresh surface, p<0.05.

[0023] FIGS. 6A and 6B shows the mean±SD number (A) and BrdU DNA
incorporation (B) of endothelial cells on NiTi surfaces after 2 and 4
days of culture. n=3. **Significantly different from the fresh surface,
p<0.01. *Significantly different from the fresh surface, p<0.05.

[0026] FIG. 9 shows an alteration in the contract angle of Cobalt-Chromium
alloy/CoCr surface with or without UV treatment. Photographic images
(side views) of 1 ml of H2O droplets pipetted onto sandblasted and
machined CoCr surfaces with or without UV treatment. **Significantly
different from the fresh surface, p<0.01

DETAILED DESCRIPTION OF THE INVENTION

[0027] According to embodiments of the present invention, it is provided a
method of generating a prohealing endovascular device, comprising
irradiating a surface of the endovascular device with a high energy
radiation for a period of time to cause the surface to become a
hydrophilic or super hydrophilic surface, generating a prohealing
endovascular device having an enhanced rate of endothelialization. The
endovascular devices have a hydrophilic or super hydrophilic surface as
opposed to endovascular devices hydrophobic nature without this
treatment.

[0028] As used herein, irradiating a surface of the endovascular device
with a high energy radiation for a period of time to cause the surface to
become a hydrophilic or super hydrophilic surface is also referred to as
hydrophilic conversion or super hydrophilic conversion of the surface.
Such hydrophilic conversion or super hydrophilic conversion of surface
(e.g., a titanium surface, NiTi surface, or CoCr surface) imparts
important technical features or advantages to an endovascular device
subjected to such hydrophilic conversion or super hydrophilic conversion
as opposed to an endovascular device that is not subjected to treatment
according to the method disclosed herein. For example, such hydrophilic
conversion or super hydrophilic conversion of surface increases the
affinity of a device with a vascular tissue, which accelerates the
healing process and reduces the clotting problem. In addition, an
enhanced affinity of the device with native vascular tissue should
decrease the level of such an adverse inflammatory reaction after the
device placement. As opposed to an endovascular device that is not
subjected to treatment according to the method disclosed herein, an
important advantage of the hydrophilic conversion or super hydrophilic
conversion of surface of an endovascular device is an enhanced rate of
endothelialization and/or neointima coverage as well as an enhanced
affinity of the device with a native vascular tissue; an enhanced rate of
endothelialization and/or neointima coverage would allow sooner cessation
of blood-thinning medications so as to reduce or minimize the risk of
spontaneous bleeding in organs such as brain and gastrointestinal tract.

[0029] Additionally, the hydrophilic conversion or super hydrophilic
conversion of surface (e.g., a titanium surface, a NiTi surface or a CoCr
surface) also reduces the friction during the insertion or delivery of
endovascular metallic devices.

[0030] As used herein, the term "enhanced rate of endothelialization
and/or neointima coverage" refers to an increase of rate of
endothelialization and/or neointima coverage of about 1% or higher, about
5% or higher, about 10% or higher, about 20% or higher, about 50% or
higher, about 75% or higher, about 100% or higher, about 200% or higher,
about 500% or higher, or about 1000% or higher at a given time after
deployment of an endovascular device described herein. Such a given time
can be, e.g., days, weeks, months, or years after deployment of an
endovascular device described herein, e.g., about 10 days, about 20 days,
about 30 days, about 45 days, about 60 days, about 120 days, about 150
days, about 180 days, about 210 days, about 240 days, about 270 days,
about 300 days, about 330 days, about 12 months, about 18 months, about
24 months, about 36 months, about 4 years, about 5 years, or about 10
years.

[0031] As used herein, the term "increased affinity" refers to an
endovascular device having an affinity of the device with a native
vascular tissue increased by at least 1% or higher, by at least 5% or
higher, by at least 10% or higher, by at least 20% or higher, by at least
50% or higher, by at least 75% or higher, by at least 100% or higher, by
at least 150% or higher, by at least 200% or higher, by at least 400% or
higher, by at least 500% or higher, by at least 1000% or higher, by a
factor of 50, 100, 1000, or 10000 times or higher.

[0032] As used herein, the term "reduced friction" refers to an
endovascular device of invention having a surface generated by the method
disclosed herein, as compared with an endovascular device without such a
treatment, having a friction during the insertion or delivery of the
endovascular device reduced by, for example, at least 10%, at least 20%,
at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at
least 80%, at least 90%, at least 95%, at least 99%, or about 100%.

[0033] As used herein, the term "reduced level of inflammation response"
refers to an endovascular device having a surface generated by the method
disclosed herein, as compared with an endovascular device without such a
treatment, having a level of inflammation response at a site receiving
the endovascular device reduced by, for example, at least 10%, at least
20%, at least 30%, at least 40%, at least 50%, at least 60%, at least
70%, at least 80%, at least 90%, at least 95%, at least 99%, or about
100%.

[0034] The endovascular device can comprise metallic or non-metallic
material. In some embodiments, the material comprises titanium, a Nitinol
alloy and/or a cobalt/chromium alloy. In some embodiments, the metallic
material can be one of gold, titanium, platinum, tantalum, niobium,
nickel, iron, chromium, cobalt, zirconium, magnesium, magnesium,
aluminum, palladium, an alloy formed thereof, or combinations thereof

[0035] In some embodiments, the method comprising irradiating the surface
of an endovascular device with a high energy source, which can be, for
example, ultraviolet light, X rays and gamma rays. In some embodiments,
the high energy radiation is ultraviolet. The period of time of
irradiation can be about 10 minutes or longer, about 30 minutes or
longer, about 60 minutes or longer, about 120 minutes or longer, about 6
hours or longer, 12 hours or longer, about 24 hours or longer, or about
48 hours or longer.

[0036] In some embodiments, upon deployment, the prohealing endovascular
device has a rate of endothelialization increased by at least 1% or
higher, by at least 10% or higher, by at least 50% or higher, by at least
100% or higher, or by at least 200% or higher.

[0037] In some embodiments, optionally in combination with the
aforementioned increased rate of endothelialization, the prohealing
endovascular device has an increased rate neointima coverage increased by
at least 1% or higher, by at least 10% or higher, by at least 50% or
higher, by at least 100% or higher, or by at least 200% or higher.

[0038] In some embodiments, optionally in combination with the
aforementioned increased rate of endothelialization and/or increased rate
of neointima coverage, the prohealing endovascular device has an affinity
of the device with a native vascular tissue increased by at least 1% or
higher, by at least 10% or higher, by at least 50% or higher, by at least
100% or higher, or by at least 200% or higher.

[0039] In some embodiments, the endovascular device of invention has a
reduced friction during the insertion or delivery of the endovascular
device reduced by, for example, at least 10%, at least 20%, at least 30%,
at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at
least 90%, at least 95%, at least 99%, or about 100%.

[0040] In some embodiments, the endovascular device of invention has a
decreased level of inflammation at a site receiving the endovascular
device of invention as compared with an endovascular device without
treatment by irradiation reduced by, for example, at least 10%, at least
20%, at least 30%, at least 40%, at least 50%, at least 60%, at least
70%, at least 80%, at least 90%, at least 95%, at least 99%, or about
100%.

[0041] In some embodiments, the various embodiments described above can
further comprise surface-treating the endovascular device prior to
irradiating the surface of the endovascular device. Such surface-treating
can be, e.g., acid-etching, sand-blasting, or machining.

[0042] In according to embodiments of the present invention, it is
provided a prohealing endovascular device. In some embodiments, the
prohealing endovascular device is generated according to the various
above embodiments of methods. The prohealing endovascular device can be,
for example, stents, grafts, stent-grafts, catheters, leads and
electrodes, clips, shunts, closure devices, valves, and particles.

[0043] In according to further embodiments of the present invention, it is
provided a method of treating or ameliorating a disorder involving a
vascular condition, the method comprises implanting in a subject the
prohealing endovascular device of the various above embodiments. In some
embodiments, the disorder is selected from the group consisting of
atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection,
vascular perforation, vascular aneurysm, vulnerable plaque, chronic total
occlusion, patent foramen ovale, claudication, anastomotic proliferation
of vein and artificial grafts, arteriovenous anastamoses, bile duct
obstruction, urethral obstruction and tumor obstruction.

[0044] As used herein, the term hydrophilic surface refers to a surface
having a water wet angle of about 0 to about 60 degrees or lower, e.g.,
40 degrees, or 30 degrees. A super hydrophilic surface refers to a
surface having a water wet angle of about 0 to 20 degrees or lower, e.g.,
about 15 degrees, about 10 degrees, or about 5 degrees.

[0045] As used herein, the term prohealing refers to attribute of an
endovascular device capable of accelerated healing without the use of a
drug or agent other than the endovascular device. In some embodiments, a
prohealing endovascular device described herein has a hydrophilic or
super hydrophilic surface.

[0048] The endovascular devices described herein can be porous or
non-porous devices. Porous devices generally have better tissue
integration while non-porous devices have better mechanical strength.

[0049] In some embodiments, the endovascular device used in the method is
selected from stents, grafts, stent-grafts, catheters, leads and
electrodes, clips, shunts, closure devices, valves, guidewires, filters,
cage-like vascular plug, coils, and particles. In some embodiments, the
device is a metallic stent.

High Energy Radiation

[0050] The endovascular devices with enhanced tissue integration
capabilities provided herein can be formed by treating the endovascular
devices with a high energy radiation for a period of time. The length of
the radiation period depends on the type of implants. For a metallic
implant (e.g., a titanium implant), the period of radiation generally
ranges from about 1 minute to about 1 month, e.g., from about 1 minute to
about 1 hour, from about 1 hour to about 5 hours, from about 5 hours to
about 24 hours, from about 1 day to about 5 days, from about 5 days to
about 10 days, or from about 10 days to about 1 month. For non-metallic
implants, e.g., a biocompatible, biodurable polymeric implant, the period
of radiation generally ranges about 1 minute to about 1 month, e.g., from
about 1 minute to about 1 hour, from about 1 hour to about 5 hours, from
about 5 hours to about 24 hours, from about 1 day to about 5 days, from
about 5 days to about 10 days, or from about 10 days to about 1 month.

[0051] The term "high energy radiation" includes radiation by light or a
magnetic wave. In some embodiments, the term "high energy" refers to a
radiation having a wavelength at or below about 400 nm, e.g., about 350
nm, about 300 nm, about 250 nm, about 200 nm, about 150 nm, about 100 nm,
about 50 nm, or about 10 nm.

[0052] In some embodiments, the radiation can have a wavelength at or
below about 5 nm, about 1 nm, about 0.5 nm, about 0.1 nm, about 0.05,
about 0.01, about 0.005 or about 0.001 nm. The radiation having a
wavelength from about 400 nm to 10 nm is generally referred to as
ultraviolet light (UV), the radiation having a wavelength from about 10
nm to 0.1 nm is generally referred to as x-rays, and the radiation having
a wavelength from about 0.1 nm to about 0.001 nm is generally referred to
as gamma-rays.

[0053] The endovascular devices can be radiated with or without
sterilization. To one of ordinary skill in the art, the endovascular
devices can be sterilized during the process of high energy radiation
(e.g., UV radiation).

[0054] In anther aspect of the present invention, it is provided a
facility or device for radiating endovascular devices. In one embodiment,
the facility or device includes a chamber for placing endovascular
devices, a source of high energy radiation and a switch to switch on or
turn off the radiation. The facility or device may further include a
timer. In some embodiments, the facility or device can further include a
mechanism to cause the endovascular devices or the high energy radiation
source to turn or spin for full radiation of the implants. Alternatively,
the chamber for placing endovascular devices can have a reflective
surface so that the radiation can be directed to the endovascular devices
from different angles, e.g., 360° angle. In some embodiments, the
facility or device may include a preservation mechanism of the enhanced
bone-integration capability, e.g., multiple irradiation of light,
radio-lucent implant packaging, packing and shipping.

Method of Treating or Preventing Disorders

[0055] An endovascular device according to the present invention can be
used to treat, prevent or diagnose various conditions or disorders.
Examples of such conditions or disorders include, but are not limited to,
atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection,
vascular perforation, vascular aneurysm, vulnerable plaque, chronic total
occlusion, patent foramen ovale, claudication, anastomotic proliferation
of vein and artificial grafts, arteriovenous anastamoses, bile duct
obstruction, urethral obstruction and tumor obstruction. A portion of the
endovascular device or the whole device itself can be formed of the
material, as described herein. For example, the material can be a coating
disposed over at least a portion of the device.

[0057] In certain embodiments, optionally in combination with one or more
other embodiments described herein, the endovascular device used in the
method is selected from stents, grafts, stent-grafts, catheters, leads
and electrodes, clips, shunts, closure devices, valves, and particles. In
a specific embodiment, the endovascular device is a stent.

[0058] Current minimally invasive interventional procedures for the
treatment of vascular diseases use a variety of metallic implant devices
such as a stent. The implantation of metallic stents following
percutaneous transluminal angioplasty has been widely accepted as an
alternative therapy to bypass surgery in cardiovascular, peripheral
vascular, and neuro-vascular interventions. Although endovascular
metallic stent implants demonstrate a great performance in human vessels,
there are some intrinsic limitations.

[0059] First limitation is a friction between a metallic device and
catheter. Usually a metallic implant is inserted into a plastic catheter,
and is pushed or twisted out of the catheter. The longer or more complex
a metallic device becomes, the more friction a treating physician
experiences during the delivery. The friction makes the delivery of stent
or coil the into a target lesion difficult and unsafe.

[0060] The second limitation is that some of the endovascular metallic
implants are biologically inactive, which delays the healing process of
the vessel that endovascular metallic devices are implanted. The metallic
device should be covered with native tissues and cells in the healing
process so that the foreign material does not have a direct exposure to
blood flow. Furthermore, delayed healing potentially causes unfavorable
event such as a stent migration.

[0061] The last limitation is that a patient who receives an
intra-arterial metallic device placement, particularly a metallic stent
placement, is required to be medicated with anti-platelet medications
such as Aspirin or clopidogrel, so called blood thinners in order to
prevent unfavorable excessive clotting. The blood thinning medications
carry a risk of spontaneous bleeding in organs such as brain and
gastrointestinal tract. Even with the blood thinning medications, the
clotting of important arteries occurs not infrequently after the
placement of metallic devices in the vessels since the devices are a
foreign material for the human vessels. The metallic device should be
covered with native tissues and cells in the healing process so that the
foreign material does not have a direct exposure to blood flow.

[0062] We describe a method that potentially overcomes the above-mentioned
limitations of endovascular devices made of NiTi. We found that
ultraviolet (UV) light treated NiTi sheet, wire, and stent have been
demonstrated to show super-hydrophilic nature as opposed to hydrophobic
nature without this treatment. This super-hydrophilic conversion of NiTi
surface may increase the affinity of a metallic device and vascular
tissue, which may accelerates the healing process after the implantation
of metallic devices. In this study, we evaluated the application of UV
irradiation to NiTi metal surface, and the difference in vitro
bioactivity with and without UV irradiation.

[0064] Bovine serum albumin, fraction V (Pierce Biotechnology, Inc.,
Rockford, Ill.) was used as a model protein. Three hundred ml of protein
solution (1 mg/ml protein/saline) was spread over a NiTi sheet surface
using a pipette. After 24 hour of incubation in a sterile humidified
condition at 37° C., non-adherent protein removed and washed twice
using saline with 0.9% sodium chloride. Two hundred ml aliquots of the
initial and removed solutions were mixed with 200 ml microbicinchoninic
acid (Pierce Biotechnology, Inc., Rockford, Ill.) and incubated at
37° C. for 60 minutes. The amount of protein was quantified by a
microplate reader at 562 nm.

Human Endothelial Cell Culture

[0065] Human aortic endothelial cells (HAOEC, Cell Applications, Inc. San
Diego, Calif.) were cultured in Endothelial Cell Growth medium. Cells
were incubated in a humidified atmosphere of 95% air, 5% CO2 at
37° C. At 80% confluency of the last passage, cells were detached
using 0.25% trypsin-1 mM EDTA-4Na and seeded onto NiTi surfaces with and
without UV treatment at a density of 3×104 cells/cm2. The
culture medium was renewed every three days.

Migration Assay

[0066] Migration of endothelial cells to NiTi surfaces was examined using
dual-chamber migration assay (345-024 K, Trevigen, Gaithersburg, Md.).
The endothelial cells were seeded into the top chamber in the culture
medium. A NiTi sample with or without UV treatment was placed at the
bottom of the lower chamber. The percentage of the cell penetrated into
the lower chamber after 2 hours of incubation at 37° C., through
polyester membrane with 8-mm diameter pores, was analyzed by a plate
reader after calcein AM stain.

Cell Attachment and Metabolic Activity Assays

[0067] Initial attachment of cells was evaluated by measuring the quantity
of the cells attached to NiTi substrates after 6 hours and 24 hours of
incubation. The cells were gently rinsed twice with PBS and treated with
0.1% collagenase in 300 ml of 0.25% trypsin-1 mM EDTA-4Na for 15 min at
37° C. A hematocytometer was used to count the number of detached
cells obtained. SEM was taken to confirm the absence of any cell remnant
on the substrates. Cellular metabolic activity was evaluated by WST-1
based colorimetry (WST-1, Roche Applied Science, Mannnheim, Germany)
after 24 hour of incubation. The culture well was incubated at 37°
C. for 4 hours with 100 ml tetrazolium salt (WST-1) reagent. The amount
of formazan product was measured using an ELISA reader at 420 nm.

[0069] Propagated cells were quantified as cell density at culture days of
2 and 4. Cells were gently rinsed twice with PBS and treated with 0.1%
collagenase in 300 μl of 0.25% trypsin-1 mM EDTA-4Na for 5 minutes at
37° C. A hematocytometer was used to count the number of detached
cells. SEM was used for the selected culture to confirm the absence of
any cell remnant on the substrates. The proliferative activity of the
cells was also measured by BrdU incorporation during DNA synthesis. At
day 2 of culture, 100 ml of 100 mM BrdU solution (Roche Applied Science,
Mannheim, Germany) was added to the culture wells and incubated for 10
hours. After trypsinizing the cells and denaturing the DNAs, the cultures
were incubated with anti-BrdU conjugated with peroxidase for 90 minutes
and reacted with tetramethylbenzidine for color development. Absorbance
at 370 nm was measured using an ELISA reader.

Statistical Analysis

[0070] All of the experiments described above were performed in
triplicates. Differences between untreated control NiTi and UV-treated
NiTi cultures were examined via t-test; p<0.05 was used as a level of
statistical significance.

Results

[0071] Conversion of NiTi by UV from Hydrophobic to Hydrophilic Status

[0072] The contact angle of H2O which was approximately 80° on
untreated control NiTi surfaces became lower than 20° after the
treatment of UV light, indicating the conversion of hydrophobic surface
to hydrophilic surface (FIG. 1). Images of the H2O droplet showed an
increased area of water spread on UV-treated NiTi surfaces (left panels
in FIG. 1).

Increased Protein Adsorption Capacity on UV-treated NiTi

[0073] FIG. 2 shows the amount of albumin adsorbed to NiTi surface during
24 hour incubation. There was a significant increase in the adherent
albumin over UV treated hydrophilic surface than over untreated surface.

Increased Cell Attractiveness of UV-treated NiTi

[0074] The number of aorta-derived endothelial cells migrated during 2
hours was over 2.5 times greater on UV-treated NiTi than on untreated
NiTi (FIG. 3). Likewise, the number of the cells attached during 6 hours
and 24 hours of incubation was significantly increased on UV-treated NiTi
(FIG. 4). The number was doubled after 24 hours of incubation. Confocal
images with the nuclear and cytoskeletal stains revealed that endothelial
cells spread more on UV-treated NiTi and the cytoskeletal development was
expedited compared with those on untreated NiTi (FIG. 5).

Increased Bioactivity of UV-treated NiTi

[0075] The number of endothelial cells at days 2 and 4 of culture was
significantly greater on UV-treated NiTi than on untreated NiTi surfaces
(FIG. 6A). Proliferation activity of the cells was also increased on
UV-treated NiTi (FIG. 6B). Metabolic activity of the cells measured 24
hours after seeding was approximately 2.5 greater on UV-treated NiTi than
on untreated NiTi (FIG. 7).

Decreased Level of Inflammatory Response

[0076] FIG. 8 shows the UV treated group elicits a markedly and
substantially lower of inflammation as evidenced by the markedly and
substantially lower IL1beta, IL6, IL8 levels elicited by the UV treated
group. What is significant about lower ILs with UV group is that UV
treatment elicits less inflammatory reactions.

Discussion

[0077] To our knowledge, this is the first study which demonstrated UV
irradiation to NiTi induces the conversion of hydrophobic to hydrophilic
surface of NiTi. The result of this study showed that the contact angle
of a water drop over the UV irradiate surface of NiTi sheet was
approximately 20 degrees, which we may call a supper-hydrophilic
conversion. Currently the inner lumen of delivery endovascular catheter
or the surface of some metallic devices has a hydrophilic polymer coating
in order to reduce the friction during the delivery. However such a
hydrophilic polymer coating comes off from the device relatively easily.
Moreover, certain devices such as a stent are not easily coated with the
hydrophilic polymers. In fact, most of metallic stents are not coated
with hydrophilic materials. The advantage of the hydrophilic conversion
of NiTi surface by UV irradiation is that it does not come off easily
unlike current polymer hydrophilic coating on endovascular metallic
devices. UV irradiation to the surface of a complex-shaped metallic
implants such as stents theoretically does not change their mechanical
characteristics. The hydrophilic conversion of NiTi may reduce the
friction between a complex-shape metallic device and catheter, and may
make the delivery of the metallic device more controllable and safer in
clinical setting.

[0078] The hydrophilic conversion of NiTi surface may bring favorable
characteristics for the use of endovascular implant. The adsorption of
proteins in the surrounding bio-fluid onto a metallic implant surface is
the first important step of our body response to the implant, since the
adsorbed protein mediates the cellular response to the implant. Albumin
is the most common plasma protein in the blood. Our data demonstrated
that the amount of albumin adsorption significantly increased over the UV
treated NiTi surface when compared to the untreated surface. This
proposes that the hydrophilic conversion of NiTi metallic implants after
UV irradiation may accelerates the healing process of the vessel where
the implant was placed.

[0079] Likewise, hydrophilic conversion may reduce the chance of
unfavorable excessive thrombus formation within the metallic implant in
vivo, since a layer of albumin minimizes the aggregation of platelets.
Our results showed an increase in bioactivity, maturity, and
proliferation of endothelial cells over the UV treated NiTi surface. UV
treated NiTi sheets were covered with endothelial cells faster than
without UV treatment. The faster coverage of metallic implants by
endothelial cells works positively on reducing the chance of unfavorable
thrombus formation. Also the faster endothelial coverage and accelerated
healing potentially makes earlier cessation of anti-platelet medications
possible, thus reducing the risk of bleeding complication associated with
those medications. The faster endothelial coverage and accelerated
healing after the placement of endovascular metallic implants also
reduced the chance of late device migration.

[0080] It is remarkable that the devices treated by UV-irradiation elicit
markedly and substantially lower inflammation responses. Less
inflammation in the tissue post-implantation indicates faster would
healing, faster endothelial/neointimal coverage over UV treated device,
lower incidence of unfavorable thrombosis or in-situ clot formation over
the metal implant surface, which are key considerations in the
intervention technologies such as stenting, etc.

Conclusion

[0081] UV irradiation to NiTi induced hydrophilic conversion of the
surface. The increase in albumin adsorption, endothelial cell
attractiveness, and bioactivities of endothelial cells indicates that the
biocompatibility of the endovascular metallic device made of NiTi is
enhanced by the UV irradiation. Our in vitro data suggests that the
affinity of NiTi with vascular tissue increases after the UV irradiation.

[0083] Conversion of Cobalt-Chromium by UV from Hydrophobic to Hydrophilic
Status

[0084] The contact angle of H2O which was approximately 80-90°
on untreated control Cobalt-Chromium surfaces became lower than
20° after the treatment of ultraviolet (UV) light, indicating the
conversion of hydrophobic surface to hydrophilic surface (FIG. 9).

Summary

[0085] The above data clearly show that UV irradiation to NiTi and
Cobalt-Chromium, two most common metallic materials used in stents,
induces the conversion of hydrophobic to hydrophilic surface of TiNi and
Cobalt-Chromium. Unlike the hydrophilic polymer coating on endovascular
metallic devices that is currently used, this hydrophilic conversion by
UV irradiation does not come off easily. The UV irradiation method helps
to reduce the friction of endovascular metallic devices such as those
made of titanium containing metal including NiTi or Cobalt-Chromium.

[0086] The above data also show that the affinity of a metallic surface
(NiTi) with vascular tissue increases after the hydrophilic conversion by
UV irradiation. The increase in albumin absorption, endothelial cell
attractiveness, and bioactivities of endothelial cells indicates that the
biocompatibility of the endovascular metallic device made of NiTi is
enhanced by the UV irradiation. The above data indicate that UV treated
NiTi devices are covered with more regenerative endothelial cells more
quickly than those without UV treatment. The increased affinity and
biocompatibility works positively for anti-clot formation on the metallic
devices, and helps to achieve a prompt healing of vascular tissue where
the metallic devices are placed.

[0087] While particular embodiments of the present invention have been
shown and described, it will be obvious to those skilled in the art that
changes and modifications can be made without departing from this
invention in its broader aspects. Therefore, the appended claims are to
encompass within their scope all such changes and modifications as fall
within the true spirit and scope of this invention.

Patent applications by Fernando Vinuela, Los Angeles, CA US

Patent applications by Satoshi Tateshima, Pacific Palisades, CA US

Patent applications by THE REGENTS OF THE UNIVERSITY OF CALIFORNIA

Patent applications in class IRRADIATION OF OBJECTS OR MATERIAL

Patent applications in all subclasses IRRADIATION OF OBJECTS OR MATERIAL